1. Field of the Invention
The present invention relates to an inertia weight which is attached to a rotary shaft for use in various apparatuses so as to achieve smooth and stable rotation of the rotary shaft, and more particularly relates to an inertia weight suitable for a driving shaft used for performing scanning by an image processor having a scanning function, such as a copying machine, a facsimile machine and a scanner.
2. Description of the Related Art
In the image processor of stationary original type, scanning for obtaining image information is performed line by line by moving a light source lamp with respect to an original placed on platen glass. A drive mechanism for moving this light source lamp uses a mechanism in which a pulley attached to a rotating driving shaft is linked with a full-rate carriage that carries the light source lamp and moves across the entire area of the original and the carriage is moved by the movement of the pulley. Besides, reflected light resulting from irradiating the original by the light source lamp needs to be guided to photoelectric converter such as a CCD (charge coupled device), and also the length of an optical path from the original to the photoelectric conversion device needs to be substantially uniform irrespective of the movement of the carriage. Therefore, in addition to the full-rate carriage, the image processor includes a half-rate carriage, which moves a half of the amount of movement of the full-rate carriage in synchronization with the full-rate carriage. Moreover, the full-rate carriage is provided with a first reflector, while the half-rate carriage is provided with a second reflector and a third reflector so that the reflected light from the original is reflected in suitable directions by the first, second and third reflectors to be guided to the photoelectric conversion device.
As described above, in the image processor, the full-rate carriage and half-rate carriage must perform accurate scanning. In order to achieve this, they are required to move in a stable manner at a constant rate. Therefore, an inertia weight is attached to the driving shaft to stabilize the rotation of the driving shaft.
The above-mentioned conventional inertia weight for a rotary shaft, however, is formed in a cylindrical or ring shape, and the driving shaft is inserted into the inertia weight when attaching the inertia weight to the driving shaft. Hence, for example, in the event of adding the inertia weight to the driving shaft or replacing it with another inertial weight, parts such as the above-mentioned drive pulley linked with the driving shaft must be detached and the driving shaft must be removed from the casing of the image processor to add or replace the inertial weight. Consequently, the operation of adding or replacing the inertia weight is complicated.
Therefore, it is an object of the present invention to provide an inertia weight for a rotary shaft, capable of being added or replaced without removing a driving shaft.
As technical means for achieving the above object, an image processor has an inertia weight for a rotary shaft according to a first aspect of the present invention, which is an inertia weight for a rotary shaft attached to the rotary shaft so as to stabilize the rotation of the rotary shaft, is characterized by comprising weight parts formed by cutting a member having an almost cylindrical shape along a plane including an axis thereof so as to freely assemble and disassemble the weight parts into and from the member having the original cylindrical shape.
In the event of adding the inertia weight, the weight parts prepared by disassembling the inertia weight in advance are attached to the rotary shaft and assembled as the inertia weight. Moreover, the assembled weight parts are fastened together or fastened to the rotary shaft with suitable securing means so as to prevent accidental disassembly. As the securing means, for example, it is possible to employ a configuration in which one of the joining faces of the weight parts positioned to face each other is provided with a female screw section, the other is provided with a through-hole, and a fixing screw is inserted into the through-hole and screwed into the female screw section so as to fasten the weight parts together.
Moreover, an inertia weight for a rotary shaft according to a second aspect of the present invention is characterized in that the rotary shaft is a driving shaft for providing a driving force for moving a light source lamp of an image processor that reads information of an image formed on a original by scanning the original while sequentially changing an irradiation position by moving the light source lamp with respect to the original.
In the image processor, the driving shaft needs to be rotated at a constant rate so as to stabilize the movement of a carriage for scanning the original, and, therefore, an inertia weight is attached to the driving shaft. Moreover, there is an occasion that the scanning condition is set by adjusting the inertia force of the inertia weight and, for this setting, the inertia weight is added or replaced, if necessary. For example, in the event of replacing the inertia weight, only by disassembling the inertia weight mounted on the driving shaft, it is possible to detach the inertia weight without removing the driving shaft. Then, the weight parts of a new inertia weight are assembled on the driving shaft and fastened together or fastened to the driving shaft with securing means or the like. Furthermore, in the event of adding an inertia weight, new weight parts are assembled on the driving shaft and fastened with the securing means or the like.
Besides an inertia weight for a rotary shaft, according to a third aspect of the present invention, an inertia weight for a rotary shaft is characterized in that the inertia weight is split into two parts. Although the number of parts into which the inertia weight is split may be changed suitably, the inertia weight is split into two parts for easy processing and simple assembling.
The nature, principle, and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings in which like parts are designated by like reference numerals or characters.